Functional influence on sutural growth. A morphometric study in the anterior facial skeleton of the growing rat.

The aim of this study was to quantify the sutural response in the various parts of the rat's upper frontal viscerocranium and study the possible effects caused by reduced masticatory muscle function. Twenty growing male albino rats were randomly divided into two equal groups: one group (Hard Diet group) received the ordinary diet in a hard pellets form, while the other (Soft Diet group) a soft diet. The experimental period started just before the rats' pubertal growth spurt (28 days old) and its duration was 28 days. After death, the heads of the animals were taken for preparation of undecalcified frontal sections, 100 microns thick. Contact microradiographs of six representative homologous sections, for every animal in both groups, were prepared. The mean width, length, height, and interdigitation ratio of the internasal, naso-premaxillary, and interpremaxillary sutures, as well as the orientation of the bony surfaces of the naso-premaxillary suture were quantified on the contact microradiographs using the IBAS automatic image analysis system. The width of the sutural space was found to be significantly greater in the Hard Diet group than in the Soft Diet group in all the sutures studied (P < 0.01). No differences in the interdigitation of the sutures were found between the two groups, except in the internasal suture in the middle part of the snout, where the Hard Diet group exhibited increased interdigitations. The bony surfaces of the naso-premaxillary suture were significantly more parallelly-orientated in the animals with reduced masticatory muscle function (P < 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)